1. Field of the Invention
The present invention relates to the field of automatic sorting and inspection systems, and more particularly to optical systems used in conjunction with automatic sorting and inspection systems.
2. Prior Art
The preferred embodiment of the present invention is intended for use in an automated bottle sorting system. Since that particular application is both illustrative of typical problems in the prior art and the solution provided by the present invention, the prior art directed to this particular application will be described.
Various types of bottle sorters are well known in the prior art, such machines being used, by way of example, for the sorting of returnable soft drink bottles. Obviously some bottles may be sorted based on bottle height and diameter and/or glass color, and accordingly, sorting machines based on various mechanical sensors and photodetectors are well known. Other machines having some form of linear array of sensors have been used to attempt to obtain more information regarding each bottle as each bottle passes the linear array. Another approach which may be expected to be used in future equipment, is to view each bottle with some form of camera system and then undertake some form of analysis of the image for identification purposes. Since the labels on soft drink bottles are almost always 180 degree labels, repeating on the other 180 degrees around the bottle, a bottle viewed from one side theoretically will present all information on the label regardless of the angular orientation of the bottle, the image portion going out of view at one side of the bottle as the bottle is rotated reappearing on the other side of the bottle. Obviously, the image will appear split, but at least the information in the image will theoretically be all there. However, in any practical system the camera must set relatively close to the bottle. Accordingly, the camera will view significantly less than 180 degrees of the bottle. Assuming that the bottles are not angularly aligned in general, not only will the image be a split image but the information in that image will now be somewhat sensitive to the bottle angular orientation, i.e., the nonviewable portion of the 180 degree image will be dependent upon the angular orientation of the bottle. The problem is aggravated somewhat by the fact that the label image is highly distorted near the edges thereof so that an additional part of the image is unsuitable for analysis and accordingly is effectively nonviewable also.
Because the useful image information presented to the camera system for any particular bottle type is somewhat bottle angular orientation dependent, a significant level of uncertainty in the bottle identification of any system will result, thereby making the sorting of bottles having similar (but not the same) labels difficult and/or subject to error. Accordingly, the preferred embodiment of the present invention is directed toward the minimization of errors from this source by providing a usable image approaching or even equal to a 180 degree wrap on the bottle being viewed.